The field of this invention relates generally to latching assemblies, and more particularly, to latching assemblies for cargo bracing devices used in cargo carrying vehicles.
Latching assemblies for extensible cargo bracing bars are well known. For example, U.S. Pat. No. 2,411,768 to Welch discloses a boxcar brace having a locking tip on a pivoted handle that engages a latch provided to secure the handle and the extended bracing members in place. Another example of a cargo bar latch assembly is that of U.S. Pat. No. 3,049,328 to Bishop. Two laterally displaceable members are telescoped to move in opposite directions when a handle is pivoted. The handle is held in place by a spring biased latch, and once the handle moves past the latch, the latch pops out into a latched position behind the handle.
Latch assemblies also can be found in a wide range of devices which include doors or windows that are latched closed. Typical of such assemblies are the latches disclosed in U.S. Pat. Nos. 3,674,329, 2,830,843, 2,637,576, 2,538,385 and 2,482,959. Such prior art latch assemblies, however, are not subjected to the same environmental stress as are cargo bar latches. More particularly, the uses to which such latches are put do not include high loading forces, stress reversals and extreme vibration.
In order to secure cargo in a trailer or rail car, a cargo bracing device must be capable of generating and maintaining substantial axial forces along the bar. Thus, the latch assembly experiences a considerable load in order to frictionally secure the bar between opposite walls of the transport container. The walls of the truck-trailer or the rail car, however, are not rigid. They flex under the dynamics of transport. In addition to the substantial load, therefore, there will be stress reversals in which the flexure of opposed wall will momentarily substantially unload the bar and then rapidly load the same.
Such stress reversals produced by wall flexure may combine with the dynamic vibrations which are constantly present in the transport container to cause unlatching of the cargo bar latch assembly. Once the bar is unlatched, it will drop to the floor of the container and be useless in bracing the load.